The ornamental design for a teabag, as shown and described.
FIG. 1 is a right-side perspective view of the tea bag showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a first perspective view, the tea bag shown in an environmental use;
FIG. 9 is a second perspective view, the tea bag shown in an environmental use; and,
FIG. 10 is a third perspective view, the tea bag shown in an environmental use.
The broken line showing of portions of the tea bag is included for the purpose of illustrating environmental structure forms no part of the claimed design.